Optical Waveguide with Interior Coupling Cavity for LED Light Mixing
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Solution Overview
Problem
Low-efficiency light coupling from Lambertian emitting sources, such as LEDs, into narrow edge waveguides in low-profile LED-based luminaires due to inherent losses in edge-lit designs.
Innovation Solution
An optical waveguide with a body of optically transmissive material having a width greater than its thickness, featuring an interior coupling cavity, an array of cavities surrounding the cavity, and a reflective surface for total internal reflection, which directs light from an LED element to extraction features for controlled light distribution and extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If edge-lit waveguide design is used to achieve low-profile luminaires, then the overall luminaire height is reduced, but light coupling efficiency deteriorates due to inherent losses in directing light from Lambertian sources into narrow edges
Solution Approach 1:
The waveguide body is segmented into multiple functional zones: an LED mounting area with a first cavity for light injection, a light mixing area with a second cavity containing a light mixing element, and a light extraction area with a third cavity. This segmentation allows optimized light management at each stage, improving overall coupling efficiency while maintaining the low-profile design.
Solution Approach 2:
A light mixing element is introduced as an intermediary component within the waveguide body. This element receives light from the LED, mixes and redistributes it, and then directs it toward extraction features. The light mixing element acts as a mediator that converts the directional light from the LED into a more uniform distribution, thereby improving coupling efficiency without increasing luminaire height.
2Length of stationary object
If waveguide thickness is minimized to achieve low-profile design, then luminaire height is reduced, but light extraction control and color mixing capability deteriorate
Solution Approach 1:
Instead of relying solely on waveguide thickness for light extraction control, the invention introduces vertical layering with multiple cavities at different depths. The first cavity receives light from the LED, the second cavity contains the light mixing element, and the third cavity manages light extraction. This dimensional approach allows effective light control in thin waveguides by utilizing the vertical dimension rather than increasing overall thickness.
Solution Approach 2:
Different regions of the waveguide body are assigned different functional qualities: the first cavity region is optimized for light injection, the second cavity region contains the light mixing element for color mixing, and the third cavity region is optimized for light extraction. This local differentiation allows each region to perform its specific function effectively, maintaining light extraction control even in minimized thickness designs.
3Loss of energy
If discrete coupling optics are used to improve light injection efficiency, then light coupling efficiency is improved, but device complexity increases due to additional components and alignment requirements
Solution Approach 1:
The coupling optics are merged with the waveguide body itself rather than being separate discrete components. The first cavity is formed as an integral part of the waveguide body, and the LED is mounted directly within this cavity. This integration eliminates the need for separate coupling optic components and simplifies alignment, while still achieving efficient light injection through the optimized cavity geometry.
Solution Approach 2:
The waveguide body serves multiple functions: it provides structural support, contains the light mixing element, manages light extraction through the third cavity, and integrates the coupling optics through its first cavity design. This multi-functionality reduces the need for separate dedicated coupling optic components, thereby reducing device complexity while maintaining injection efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances light mixing and extraction efficiency, achieving improved color mixing and control over the emitted light with minimal waveguide thickness, resulting in a more uniform and collimated light output.
Implementation Method 1
a total internal reflectance optical member disposed in the interior coupling cavity
Implementation Method 2
Discrete coupling optics use refraction, total internal reflection, and surface or volume scattering to control the distribution of light injected into the waveguide
Implementation Method 3
Discrete coupling optics use refraction, total internal reflection, and surface or volume scattering to control the distribution of light injected into the waveguide
Implementation Method 4
Discrete coupling optics use refraction, total internal reflection, and surface or volume scattering to control the distribution of light injected into the waveguide
Data Source
AI summary
An optical waveguide includes a body of optically transmissive material defined by outer edges and having a width substantially greater than an overall thickness thereof. The body of optically transmissive material includes a first side and a second side opposite the first side. An interior coupling cavity is defined by a surface intersecting the second side and extends from the second side toward the first side. The interior coupling cavity is disposed remote from edges of the body and is configured to receive an LED element. The body of optically transmissive material further includes a first array of light mixing cavities surrounding the interior coupling cavity and an extraction feature disposed on one of the first and second sides. The light extraction feature at least partially surrounds the interior coupling cavity.